Recent progresses of video technologies include development of video systems for providing a video (stereoscopic video), which is stereoscopically perceived by a viewer. Such a video system typically comprises a display device configured to display a video including a left frame image to be viewed by the left eye and a right frame image to be viewed by the right eye, and an eyeglass device configured to assist in viewing the video, which is displayed by the display device (for example, refer to Patent Document 1). The display device sends a synchronization signal, which synchronizes with the display of the frame images of the video while the eyeglass device executes the stereoscopic visual assistance for assisting in viewing the video in response to the synchronization signal. As a result of the eyeglass device executing the stereoscopic visual assistance which synchronizes with the display of frame images of the video, the viewer may stereoscopically perceive the video displayed by the display device.
The eyeglass device worn by a viewer typically looks like eyeglasses for correcting vision. It is suitable for such usage of the eyeglass device in general to utilize a compact and portable battery as a power source of the eyeglass device. It becomes less likely that the stereoscopic visual assistance keeps up with the display of the frame images of the stereoscopic video which the viewer views if the stereoscopic visual assistance of the eyeglass device decreases the battery power too much. It is less likely that the viewer wearing the eyeglass device identifies a failure in the stereoscopic visual assistance of the eyeglass device, which is caused by shortage of the remaining battery power. Consequently, the viewer may not comfortably enjoy the stereoscopic video.
As another failure of the eyeglass device, there is a communication failure of the synchronization signal between the display device and the eyeglass device. If the communication fails, the eyeglass device of Patent Document 1 allows light to be transmitted to the left and right eyes. Consequently, the viewer may continue to view the video even during the communication failure.
The control for allowing the light to be transmitted to the left and right eyes during the communication failure, like the eyeglass device disclosed in Patent Document 1, enables the viewer to view the video, but the viewer may no longer stereoscopically view the video. Since the viewer can still view the video, it becomes less likely that the viewer becomes aware of the occurrence of the failure in the eyeglass device. Accordingly, the viewer may not comfortably enjoy the video.
Used hours of the eyeglass device may be also exemplified as information to be communicated to the viewer, in addition to the aforementioned information about failures, which occurs in the eyeglass device. Prolonged use of the eyeglass device may make the viewer's eyes excessively tired.
Patent Document 1: Japanese Patent Application Laid-open No. H6-46460